The present invention pertains to the decontamination art. It finds particular application in conjunction with sterilizing medical equipment and will be described with particular reference thereto. It will be appreciated, however, that the invention is also applicable to disinfecting systems as well as to microbially decontaminating a wide range of items, including medical and dental instruments, laboratory equipment, industrial equipment, and the like.
Disinfection connotes the absence of pathogenic life forms. Sterilization connotes the absence of all life forms, pathogenic or not. Often, sterilization is measured against the elimination of bacterial endospores which are the living organisms most resistant to conventional sterilants. Microbial decontamination is used herein as the term generic to both sterilization and disinfection.
Many hospitals and larger facilities have a central sterilizing area. Medical equipment to be sterilized is forwarded to the sterilizing area where it is processed by trained technicians and returned to the individual medical units. One problem with a central sterilizing area is that the turnaround time on sterilization is relatively long, often on the order of days. This long turnaround time increases the need for duplicate sets of medical equipment, sufficient numbers of sets that a sterilized set is available for each patient during the turnaround time. Another drawback of the central sterilization area resides in the complexity of transporting and sorting equipment, the storage areas required, and the space required for a central sterilization facility. Like medical instruments tend to be interchanged such that physicians who send well cared for equipment for sterilization often receive mistreated equipment in return. A result and perhaps greater problem is that equipment is not always sent to a central sterilization facility before it is reused.
Commonly, medical equipment is sterilized in a steam autoclave. Autoclaves kill like forms with a combination of high temperature and pressure. Steam autoclaves have several drawbacks. The high temperature pressure vessel tends to be relatively bulky and heavy. The high temperature and pressure tends to dry or curtail the useful life of endoscopes, rubber and plastic device, lenses and other portions of devices made of polymeric materials, and the like. Further, the sterilizing cycle is relatively long from the start of the cycle until the instruments are cool enough to use.
More sensitive medical equipment is often sterilized with an ethylene oxide gas system which is thermally less severe than steam. However, the ethylene oxide has several drawbacks. First, the instruments must be exposed to the ethylene oxide for a relatively long time, on the order of 31/2 hours. Thereafter, an 8-12 hour degassing period is normally required for removing absorbed ethylene oxide from plastic and other ethylene oxide absorptive materials. The pressure and depressurization cycles of ethylene oxide sterilization may damage lens and other delicate instruments. Second, the ethylene oxide is relatively expensive. Third, ethylene oxide is sufficiently toxic and volatile that extensive precautions and training are commonly taken to assure operator safety. Usually, a trained operator and a dedicated facility are required.
Liquid sterilization systems are often used for heat-sensitive and other delicate instruments. Commonly, a technician mixes a liquid sterilant composition and manually immerses the items until he deems them sterilized. The high degree of manual labor introduces numerous uncontrolled and unreported variables into the sterilization process. Manual timing of the immersion raises assurance problems that the item was immersed for a sufficient duration. Further, sterilants tend to weaken, i.e. have a limited shelf life. Variations in the duration between when the technician mixed the sterilant and actually used it also raises problems with sterilization assurance and reproduceability of the microbial decontamination.
Another problem with the prior art liquid system resides in the corrosive nature of the strong oxidants that are commonly used as liquid sterilants. Normally, the sterilized items are rinsed to remove chemical residues. This rinsing also adds a variable that reduces the assurance the item has been disinfected or sterilized. Once rinsed, the item is susceptible to reinfection by airborne microbes.
In accordance with the present invention, a new and improved sterilization apparatus and method are provided which overcome the above-referenced problems and others.